Hydrazo compounds and inversion thereof



Patented Apr. 23, 1935 UNITED STATE PATENT OFFlCE liroaazo coMroUNINVERSION a a THEREOF William S. CaIcott, Pennsgrove, and Frederick B.vD nin and Norma 6. Seniors, Gamers Poin J assigno to I- u P nt e Nemours& Company, Wilmington, DeL, a, corporation o Delawar NoDrawingApplication June28, 1930,

' Serial No. 464,702

1" 2r Ql'ainis. r01. maniacs) This invention relates to hydrazocompounds and their production, from nitro-benzenes. It i also relatesto the inversion of hydrazo-benzenes to benzidines. More particularly itdeals with r the formation of hydraze-benzenes in a new Cain & Thorpe,1918, page 22).

The general course of this reduction reaction; is well understood, forexample it has beenpointed out that the alkaline reduction ofnitrotoluene (a representative of this class) takes thefollowing course(Zeit. Ang. Chem. 13, 135).

. Nitro-tolucne Nitroso-toluene Tolyl-hydroxyI amine When the alkaline.reduction of nitro-lbenz enes to hydrazo-benzenes by means oi zinc, andcaustic is carried out in an aqueous a very 7 poor yield is obtained,70% or more of the final It is also known that the.

of hydrazo-benzenes it involved the additional expense of alcoholrecovery.

Izmailskii (U. S. 5. Russia Paton 116 of Feb. 28, 1925) and NelsonandPrasial (U. S. Patent 1,644,484 of October 4, 1927) have recentlysuggested that this reduction be performed in'the presence of a solvent;not miscible with water. This method gives better yields than are0btained in anraqueous medium but like the reaction in anra'lcoholicmedium mentioned above involves the cost of solventrecovery.

As a third alternative, the reduction may be carried to the amt-benzenestage or somewhat further, without the use of any solvent or dil uentwhatever, other than the water introduced with the caustic solutionusedto activate the zinc; this water being less than 10% of the weightof the nitro-body. By the azo-benzene stage; it is intended to refer tothat portion of the reaction where the amount of the azobenzene presentis near the maximum; or where the melting point of the mixture begins torapid- 1y approachll5' C. After this stage is reached as the reduction.continues, the freezing point of the charge rapidly rises, and it istherefore necessary to introduce some diluent with which the wellagitated mass may-be mixed to avoid its solidifying (at the reductiontemperature desired), into arigid cake and thus stopping the reduction.It has been customary, therefore, in this method, to add to the wellagitated reduction mass, when its melting point begins to rise rapidly,an amount of hot water from once to twice the weight of thenitroetoluene charged... Thereafter the reduction has been completed byfurther addition of zinc and; sodium hydroxide, yielding pellets ofhydrazo-toluene together with zinc sludge These pellets have the form ofirregular granules averaging from 1 to- 3- diameter; l l

When the inversion to henzidines is made by treatment with acid (forexample, hydrazo-toluone to tolidine), the reactions chiefly occurringHydrazo toluene Ditolyline on; 0H; on o Er Ha L Tglifiill i QHa CH! Ithas been found that the hydrazo-benzene pellets, produced according tothe prior art, due to their density, smooth surface, and form, areentirely unsuited for economical inversion to benzidines by treatmentwith acid, the reaction being extremely slow.

For this reason, in the past it has been found advantageous to invertthe hydrazo-benzene by one of two general methods. .According tothe.

first the difiicultly reactive pellets have been dissolved in a solventand by the second they have been disintegrated preparatory to treatmentwith acid. Both methods are inherently expensive and involve losses byoxidation of the hydrazo-ben- .zene. In the solvent method the pelletshave been dissolved in some substance such as alcohol, solvent napthaorbenzene and agitated with aqueous acid of suitable strength. This methodinvolves the expense of solvent recovery and yields comparatively largeportions of di-tolyline. In the pellet, disintegration method an attemptto decrease the oxidation losses of hydrazo-benzene in grinding has beenmade byutilizing apparatus which excludes air. This is an additionalcause for expense. Whether disintegrated in the presence or absence ofair the treatment of the hydrazo compoundwith acid hasrusually followedas quickly as possible to further decrease the'loss by oxidation.

It is obvious, therefore, that the prior art methodsillustrated above,all possess undesirable and disadvantageous characteristics.

This invention has for an object the preparation of hydrazo-benzenes ina new physical form 'and improved methods for producing such compounds.Other objects are to devise new processes for the preparation ofbenzidines and to devise processes which will increase the yield andquality of hydrazo-benzenes and benzidines. Other objects will appearhereinafter.

The above objects are accomplishedby the present invention whereby thereduction of nitrobenzenes to hydrazo-benzenes is. carried out in thepresence of a protective colloid and whereby the. resultanthydrazo-benzene is inverted to a benzidine in the presence of a mineralacid.

It was shown above that in the production of hydrazo-benzenes, thereduction of nitro-benzene to the azo-benzene stage or further may becarriedvout without the addition of any solvent or diluent. It has nowbeen discovered that if,

at this stage, a quantity of water be added sumcient to carry thereduction products in suspension and containing an amount of protectivecolloidsuflicient to form an emulsion of the reduction products in thewater, the reduction may then be completed by further additions of zincand caustic with numerous advantages. Theinvention will be readilyunderstood from the consideration of the following examples.

Example '1 0.2% aqueous soap solution a't"100 c-qwer'e rap-. idly addedand the reduction continuedby the addition of more zinc until thereduction mass was a light gray color, showing that the hydrazo stagehad been reached.

The hydrazo-benzenes produced by the process set out above may besubstantially freed from zinc-hydroxide by treatment with sulfuric acid.This will be clear from the following explanation.

The slurry resulting from the above process was Example II Into a vesselprovided with an agitator and cooling coils was charged 10% hydrochloricacid by weight, in about excess of that theoretically required for theinversion. This acid was cooled to 0 C., and into it was shovelled,graduallywith good agitation the moist, highly dispersedhydrazo-toluene, the temperature being kept under 10 C. until inversionwas complete, as shown by chemical tests. after which the charge washeated to 70 C. and sufficient water added to dissolve thetolidine-hydrochloride. After this point the tolidine was freed from thetoluidineby precipitation of tolidine sulfate and filtration. The basewas then formed with sodium carbonate in the customary and well knownway.

The protective colloid preferred is usually some water soluble salt of afatty acid commonly termed a soap. Other protective colloids may be usedhowever for example, a member or memers of the group exemplified byTurkey red 01], glue, casein and the water soluble fraction of sludgeacids (such as result from the treatment of petroleum oils or fractionsthereof with sulfuric acid). The strength of the water solution of theprotective colloid may vary but the solution need not ordinarily containmore than 5% of the colloid.

In the separation of the zinc from the hydrazobenzenes the reactions maybe carried out at ordinary or reduced temperatures. The preferredstrength of sulfuric acid is from 10 to 20% although stronger or weakeracid may be used if desirable. The length of treatment with the sulfuricacid may be varied as desired although usually 20-30 minutes sufiicesfor solution of the zinc. The minimum amount of sulfuric acid is thatmolecularly necessary to change the zinc present to zinc sulfate, butordinarily an excess of acid is used. The excess should be as small aspossible due to its effect on the hydrazo body and under usual operatingconditions 25-50% excess is sufficient.

The quantity and identity of the mineral acid used for the inversion mayvary, but it is preferred to use hydrochloric acid in concentrations offrom 5 to 20% by weight. The use of nitric or other oxidizing acid isnot permissible. It is to be understood that otherconcentrations andother mineral acids may be used. Preferablythe temperatures usedforinversion are below 10C; Y r

'Whil thisinvention is not limited to any benzidines:..

a p 7 V v V reac es: specific" ,nitro-benzene certain'nitro bodiesconcerning which thislinvention has particular imf portance are:Intro-benzene, nitro-toluene,".ni-v

tro-anisol, and their hornologues; i

' The invention herein disclosed has numerous advantages among which areconvenience. crop oration and substantially quantitative yields "of Thehydrazo-benaene producedthisprocess isjin the form of extremely fineparticles readily oseparableby filtrationxand, capable of. being in-'verted by an aqueous acid with great speed and v with improved yields.-This productfmayornore over-he handled commercially with great'freeiiomofj ,OXt-datio'n probably due to the protecting ac-v tion ,ofthe thin.coat of colloid whichiadheresto r ITrisinventionavoids siredto -limitittherebyQ I a -1 As many apparently widely difierent embodi .mentsof'this invention maybe made without. 1 departing from the spirit andscope thereof, it isto be understood that we do not limit ourselves,

the particles.

While certain theories have been :set out to aid in understanding theinvention itis not deto; the specific embodiments thereof. except asdefined in the appended claims. 1

We claim: i I

1. The process comprising adding to about 10% parts of.ortho-nitro-toluene, small increments of zinc and a dilute solution ofalkali-metahhydrox ide vlilelmaintaining the temperature at about lOll Cto about 115 0., until the nitro-toluene has been reduced to the,ace-toluene.,stagefaddingf aoout 200 parts of an aqueous approximately,

2% soap solution whichihas a temperature of 'about 19;)". C.,;ccntinuingtheaddition of zinc'and alkaliemetalhydroxide until the charge hasbeenreduced to the 'hydrazo-toluen'e stage, Washing the resultant productwith'about lQ-2G% sulfuric o acid for from 2fi-3iltminutes; at notgreaterthan ordinary temperatures, thereafter adding the said product;in small increments to an approximately 10 hydrochloric acidsolutionheld at about 0 10,, the" said hydrochloric acid being in anamount. about twice that, theoretically necessary to convertthefhydrazo-{toluene compound. to

C.' to about C until the nitro benzene L hasbeen reduced to'theazosbenzene stage adding about 200 parts oi an aqueous approximately 2%.

soap solution which has atemperature of about 100 C., continuing theaddition of zinc and alkali-Inetal hydroxide until the charge has beenreduced to the hydrazo-benzene stag'eQweshing H the resultantproductwith about l,0%20% sulfuric acid for from 20-30 minutesat notgreater than ordinary temperatures, thereafter adding the saidproduct'in small increments to an approximately 19% hydrochloric acidsolution held at about 0 ,C., the said hydrochloric acid being in anamount about 200% of that theoretically necessary to convert thehydrazo-benzenecompoundto a ben-' zidine, maintaining thetemperaturebelow about J I 10 until the inversion to the benzidine is sub- 3thereon; H g a, V V V w f 55l-Iydrazo-benzenes in thflfilllll of huepar,- iticles and having a'coating oi soap thereon.

. w '6. In the'pro'cess of inverting'hydrazo-benzenes the steps orfinely dividing the hydrazo-be n zen'e r the necessity of disintegr'ation oi'thesolid hydrazo-benzenes and the reccvery oi solventsfromthe variousstages of the reaction. Y

; face thereof whichfis substantially stantially complete and separatingthe benzidine compound; a 3Hydrazou toluene in the form offineparticles;

-' having acoating; of soap thereon and character izedby greatfreedcmirom oxidationj- L er'l-Iydrazo-benzenes intheiorin of fine particlesand having a coating of a protective'col ida-nd coating' thesurface of the particles'gwith a protective colloid.

7; The processor producing hydrazo-toluene which comprises treatingorthc-nitre-tcluene with sufncient this and dilute alkali to convert it7 to the azo toluene stage While maintaining the temperature at about100 C'. to about;ll 5 C thereafteradding an aqueous solution of a pro--tective colloid, continuing the reduction" to hydraso-toluene, andseparating "the: hydraa toluene. i

8'. The processor producing hydrazo-be'nzenes which co'inprisestreatingnitro-benzenes with suificient'zinc and dilute alkali to'corivert themto the azc benaene stage while};maintaining the: temperature at alooutC.'to about 115. 0.,

thereafter adding an aqueous solution of aproi tect'ive colloid,continuing the reduction tohydrazo-henzenes; and separating the hydrazobem 9. The 'hydra'zo toluene body in the form of particles having aprotective colloid on the suridentical with that resulting ircm theprocess of producing hydrazo-toluene which corn-prises treatingorthonitro-toluene with sufilcient zinc and dilute alkali to convert itto the arc-toluene stage while rnain- -t tairnngthe temperature ataboutC. to about 115 C., thereafter adding an'aqueous solutionofa'prfotective colloid, continuing the reduction to hydrazo-toluene,and separating the hydrazotoluene body. 7 r l 1G. The hydrazo benzenebod-y the form of particles-having a protective colloid on the sur-'face therecf'which is substantially identical with that. resulting fromthe process of producing hy draZo-Toenzenes which coniprises'treati'ngIntrobenzenes with suflicient Zinc and dilutealkali to convert saidnitro-henz ene to the 'azo benzen'e st-age'while maintaining thetemperature at acout 106 (1. to about1l15 Q, thereaiter adding' an'aqueous solution of a protective colloid, continuing the reductiontoJhydrazo-b'enzenes, and separating the hydrazo-benzene bod-y.

11.1The processor obtaining high yields of ,hydrazo-benzenes fromnitro-henzenes compris 'ing treating a intro-benzene with increments oizinc and dilute'alkalnmetal hydroxide to-reduce it totheazo-benzenestage; addinga protective colloid in water and continuing the additionof .zinc and hydrox de until a hydrazo-benzene is produced and thenseparating it;

I 12. The process of obtaining high yields ofhydrazo-benzenesfrom nitrobenzenes 'comprising treating a nitrobenzene withincrements of zinc anddilute alkali metal hydroxide to reduce it to the aZo-benzene stage, andadding water containingrwater'soluble soap.

13. The process of obtaining high yields of hydrazo-benzenes fromnitrobenzenes comprising'treating a nitro-bnzene with increments of zincand dilute'alkali-metal hydroxide to reduce it to the azo-benzene stage,adding a. soap solu-.

tion andcontinuing the addition of. zinc and hy-' droxide until ahydrazo-benzene is produced and then separating it. I

14. The process of obtaining, high yields of hydrazo -benzenes fromnitro benzenes comprising treating a nitro-benzene with increments ofzinc and dilute alkali-1netal hydroxide to'reduce it to the azo-benzenestage, and adding a soap solution of concentration less than 5% andcontinuing I the treatment with zinc a'nd hydroxide to form thehydrazo-benzen'e. I 1 I "15. The process of obtaining high yields ofhydrazo-benzenes from nitro benzenes comprising treating a intro-benzenewith increments of zinc and dilute alkali-metal hydroxide to reduce itto the azo-berizene stage, adding a dilute soap solution in an amountsurficient' to cause, the

hydraZobenZene to be formed in small particles and continuing thetreatment with zinc and hydroxide to form the hydrazo-benzene. v

16. The product which is substantially identical with thatresulting fromthe process of obtaining high yields of hydrazo-benzenes fromnitrobenzenes comprising treating a ,nitro-benzene with'increments ofzinc and dilute alkali-metal hydroxide to reduce it to the azo-benzenestage,

' adding a'dilute soap solution in an amountsufsmall particles andcontinuing the addition of zinc I ficient to cause the hydrazo-benzenetobe formed in small particles. I

17. The method ofproducingimproved yields of finely divided, oxidationresistant hydrazoe toluene comprising treating nitro-toluene withincrements of zinc and dilute alkali-metal hydroxide to reduce it to thealso-toluene stage, adding a dilute soap solution in an amountsufficient to cause the hydrazo-toluene to be formed in andhydroxideuntil arhydrazo toluene is produced and'then separating it. 18. Themethod of producing improved yields of finely divided, oxidationresistanthydrazm' benzenes comprising treating nitro-toluene withincrements of zinc and dilute alkali-metal hye droxide to reduce it tothe azo-toluene stage, add-v ing a dilute soap solution in an amountsufficient to cause the hydrazo-toluene to be formed in small particlesand continuing theadditionof zinc and hydroxide until a hydrazo-tolueneis produced and then separating. it.

19,1-Iydrazo-benzenes in the form of fine particles having a coating ofa protective colloid thereon and-characterized by great freedom fromoxidation. I y I 20. The process of producing. hydraZo-toluene whichcomprises treating ortho-nitro-toluene with sufficient zinc and dilutealkali to convert it to thegazo-toluene stage while'maintaining thetemperature at about 100 C. to about 115 0.. thereafter adding anaqueous solution of a protective colloid, continuing the reduction withzinc and dilute alkali to hydrazo-toluene, and separating thehydrazo-toluene.

21. The process of producing hydrazo-benzenes which comprisestreating anitro-benzene with sufficient zinc and dilute alkali to, convert it tothe azo-benzene stage While maintaining the temperature at about 100 C.to about 115 C., thereafter adding an'aqueous solution of a protectivecolloid, continuing the reduction with zinc and dilute alkali tohydrazo-benzenes, and separating the hydrazo-benzenes.

' 22. The hydrazo-toluene body in the form of particleshaving aprotective colloid on the surface thereof which is substantiallyidentical with that resulting from the process of producinghydrazo-toluene which comprises treating' lorthonitro-toluene withsufiicient zinc and dilute'alkali to convert it'to the azo-toluene stagewhile maintaining the temperature at about 100 C.

to. about 115 0., thereafter adding an aqueous 7 solution of'aprotectivecolloid, continuing the re-v duction with zinc and dilutealkali to hydrazotoluene, and separating the'hydrazo-toluene body. 23,.The hydra'zo-benzene body in the form of particles having a protectivecolloid on the surface thereof which is substantially identical withthat resulting fror'n'the process of producing hydrazo'-benzenes whichcomprises treating ni-' tro-benzenes with sufficient zinc and dilutealkali to convert said nitro-benzene to the aZo-benzene stage whilemaintaining the temperature at about 100 C. to about 115 C., thereafteradding an aqueous'solution'of a protective colloid, continuing thereduction with zinc and dilute alkali to hydrazo-benzenes, andseparating the hydr-a'zobenzene body.

24; Hydrazo-benzenesin the form of fine particles having thereon acoating of a protective colloid from the group consisting, ofsoap,Turlceyred oil, water soluble sludge acid fraction, glue andcasein; r

25..'In the process of inverting hydrazo-benzenes by treatment withnon-oxidizing mineral 'Iurkeyred oil, glue, water soluble sludge acidfraction and casein. II I 27. In' the process of invertinghydrazo-benzenes by treatment with non-oxidizing mineral acids, thesteps comprising finely dividing the hydrazo-benzene. and coating thesurface of the particles with Water soluble sludge acid fraction. I

WILLIAM S.'CALCOTT.

' FREDERICK B. DOVVNING.

NORMAN C. SOMERS.

